PROJECT SUMMARY Recently, single particle cryo-electron microscopy (cryo-EM) combined with 3-D reconstruction has emerged as a revolutionary tool for solving high-resolution 3-D structures of viruses and macromolecular complexes. The rapidly increasing number of near-atomic resolution (3-4?) structures solved using cryo-EM has allowed unprecedented atomic level understanding of fundamental cellular processes and viral infections. To obtain near-atomic resolution cryo-EM structures, requires the collection of high-resolution image data using state-of- the-art imaging resources, including both a high-end transmission electron microscope and a direct electron detector. The direct electron detectors not only improve image resolution and contrast, but also record movies for subsequent computational correction of electron beam-induced, sample movements during exposure. The increased image contrast and resolution are essential for solving near-atomic resolution structures of small protein complexes. However, the high cost to purchase and maintain a state-of-the-art cryo-EM resource, with both a high-end electron microscope and a direct electron detector, precludes many cryo-EM investigators from having access to these new techniques. Here, the creation of a Midwest Consortium for High- Resolution Cryo-electron Microscopy is proposed to provide access to such high-resolution data collection capability for cryo-EM laboratories without access to such resources. This consortium will consist of 4 investigators from the host institution (Purdue Univ.) which will maintain the high-resolution data collection resource (Titan Krios 300kV FEG microscope with phase plate, energy filter, and direct electron detector) and will provide services to 11 investigators from 10 partnering institutions (Boston Univ. School of Medicine, Michigan State Univ., Penn State College of Medicine, Rutgers Univ., Univ. of Alabama at Birmingham, Univ. of Colorado Boulder, Univ. of Kansas, Univ. of Missouri, Univ. of Vermont, and Virginia Commonwealth Univ.). The collective experience of the Purdue facility staff, faculty and onsite service engineer, in high-resolution cryo-EM imaging, will ensure that the facility operates at peak performance with minimal service interruptions. The high-resolution data collection capabilities established at Purdue and accessible to the partnering labs, will allow these investigators, who are all, except for the 3 new investigators, NIH-funded, to overcome the resolution barrier and facilitate discovery within their own cryo-EM projects on a range of structures, such as, bacterial pathogen adhesion proteins, human viruses, Huntington's Disease proteins, synaptic vesicle proteins, chemoreceptor signaling complex, etc. The Consortium will provide comprehensive support to the cryo-EM projects, including shipping samples, preparing sample grids, collecting high-resolution single particle and tomography images, processing raw movies, and transferring data back to the partners' labs. The data collection services will range from full data collection where partners simply mail in the samples and then receive the image data, to hands-on operations of the cryo-EM by partners trained by the host facility's staff.